Fuel theft was a big problem. That's precisely why they went to pre-pay... because people, given the chance, are dishonest. Don't blame the gas stations, blame the lowlifes who stole all the gas for so long. If they weren't busy stealing gas, pre-pay wouldn't have been necessary.
These days almost everyone buys gas with a card anyway... credit or debit. So pre-pay isn't even an issue. You swipe your card, you pump your gas. Done. Makes perfect sense to me. Why trudge over to the building and pre-pay when you can just use your card right there at the pump?